I just acquired a 4000 series near Toronto and upon firing up the PSU (not connected to the console, just in case) I noticed a resistor caught on fire and the +18 side went out, as shown from the front panel. The PSU overall looks pretty rough, and someone's been in there to do some work after a major fire burned a massive hole into the circuit board. I was assured that it worked, but I'm not surprised that it doesn't. However, I have manuals and documents but no schematics or anything on the PSU.

Does anyone have anything for me? And, I'm curious if anyone rebuilds these from scratch. We had our TAC Magnum PSU rebuilt this year from GRS Systems in LA and it was probably the best thing we could have done for that console - all the hum and strangeness issues that happened totally disappeared!

I just found a document that lists all the parts in the PSU. However, the PCB is not labelled in any way whatsoever, and looks rather homemade. I've attached a pic that shows which resistor burned out on what I believe is the +18 side, but I can't tell what value it is:

It seems that the chips installed are newer than the ones listed in this pic - is it possible that these "newer" chips caused the resistor to fry?

I found a cool resistor calculator Widget and iPhone app - I've always been really bad at seeing the colours, but fortunately the previous owner sent me this large image. The burnt out resistor appears to be a 470 ohm, from what I can tell. I'll stick a new one in and put the original IC's in there as well, just in case those are the reason it blew in the first place.

If anyone else is interested in the app, it's free, and here's the link:

Hi, I know this is a really old post, but was just wondering why you didn't have GRS repair your PSU? You said they rebuilt your other PSU. I know they work on D&R consoles and PSU's, having seen a few in their shop the past few months.

So, an ongoing project this clearly is. We're looking at putting this little guy into a new room, and I'm now back to rebuilding it. GRS will do a full premium rebuild for $360 on the PSU. My concern is, could it still be underpowered? If we're spending that much money, should we just get another larger/better PSU? What would be the best option here?

Man, I would just buy a new PSU with more current output! Just looking at your PSU makes me nervous and why pump that much cash into that PSU.! LOL! Sorry.

GRS had a flyer out last mont on a bunch of used rebuilt power supply systems they were selling. They had some larger 10, 12 and 16 Amp systems for sale that were pretty reasonable. I believe these were trade in systems.

what is this yellow guy in the lower left corner? My PS definitively doesn't have it - there's a straight connection between PCB and chassis. I assume, the yellow guy is some kind of mod to prevent hum. Could you tell me his specs?

My PSU is back up, and seems to be doing ok. The 2N3055's get hot when the entire console is running, but I'm not sure if that's normal...had a couple channels that were killing things, and those are now disconnected. Ya, I'd def not put any money into this PSU - beyond the couple bucks I've spent in parts fixing it. I've emailed GRS about a new PSU, but what's the deal with that place? One day you'll get emails, then they ignore you forever. Maybe they just don't have enough staff to answer emails or something, but jeez, it's really weird.

I have no idea what that little yellow guy is - some kinda grounding scheme of some sort. I wish I could tell you more...